The dark atmosphere in your intro is perfect for a boss fight lead-in. I love the piano melody that comes in at 0:29, as this really sells me on the Halloween theme. The intense drums and organ work so well together to suddenly jump into the intense beginning of the fight. The transition into the second part of the song is very well done and feels really big! Following the big crash is a section that is a little more subdued than I expected, but that seems to make the boss feel a little more creepy and works really well for the spooky intention. Great work and thank you for sharing!